battery backup 520t issues

Ive just installed the battery back up and when disconnecting the main car battery the alarm doesn't trigger but when i reconnect the battery the alarm is triggered. Also another note is i have a Capacitor which i think is causing the issue. If so whats a way around it? Here is how its installed gray wire > brain 12v black > constant ground red wire > constant 12v blue wire > trigger

Also i was wondering about changing the sealed battery because of issues of its capacity. Here is the battery im looking at replacing it with.

Your connections are correct. The capacitor should have no affect.  If you have a volt meter, double check the battery backup pack to make sure it shows at least 12 volts. If you have a -hood pin switch connected to the same -blue input, it will not activate the alarm when the hood is open you activate the alarm. Try holding down your pin switch and arming the alarm...then disconnect the battery. It should then activate. If you arm the alarm with the hood open it will bypass that -input zone if the 520t is also connected to it. So give it a try and let me know.